It's the latest step in a midcareer makeover that has catapulted Cooper, 38, from throwaway films like The A-Team to the A list, front and center in the vanguard of a new generation of leading men.

Cooper's dashing good looks led to years of typecasting as cocky cads (notably the conceited, adulterous hothead in Wedding Crashers) and generic boyfriends. Remember him in He's Just Not That Into You? Neither does anyone else.

The Hangover series earned hundreds of millions of dollars and made Cooper a bona fide megastar, but it was not much of a showcase for his abilities.

"It wasn't even until Silver Linings Playbook that I realised how many people didn't think I was an actor," Cooper said in a recent phone interview. "Maybe I, like Richie DiMaso (the befuddled FBI man he plays in Hustle) was in a bit of a delusion."

More likely, the people who underestimated Cooper were wrong.

In 2012's Silver Linings Playbook he played a manic depressive who assaults his wife's lover, then moves in with his parents after months in a mental hospital. His performance, which turned this borderline psycho into a lovable romantic mutt, earned Cooper a best actor Oscar nomination.

Since then, he's earned terrific notices as a naive rookie cop who goes on to become a self-serving politician in The Place Beyond the Pines. He also played The Elephant Man last year at the Williamstown, Massachuetts, Theatre Forum, and hopes to repeat the role on Broadway.

Even before director David O Russell wrapped production on Silver Linings Playbook, he recruited Cooper to star in American Hustle, his follow-up film.

Cooper, Jennifer Lawrence, Amy Adams, Christian Bale and Robert De Niro play schemers double-crossing their way through a back-stabby scheme inspired by the Abscam scandal. In that 1978 sting operation, federal agents busted politicians who accepted bribes from an actor playing a Mideast sheik.

Cooper's character is an FBI operative who cons two con artists into working for him. The gullible lawman soon finds himself in over his head strategically, ethically and romantically. Cooper and Russell made it their main goal to demolish the stock character of the FBI antagonist in their delirious crime story.

"We wanted to reinvent that archetype completely," Cooper said. "We wanted Richie to be almost as colorful as the Irving character" - a whiny, tubby swindler played by Christian Bale, wearing a Donald Trump comb-over and packing a Santa Claus paunch.

Irving's scams include keeping a fake-English mistress (Adams) under the radar of his wife (Lawrence). For a while, anyway. The film morphs into a screwball love story, with the conniving players switching sides faster than a flipped coin.

Cooper calls Russell, who co-wrote the script, an "idiosyncratic," hard-charging filmmaker who treats his projects like all-in sports contests. Every aspect of the characters was thought out in detail, down to the point that the boyish Richie is never seen with his tie properly tied until a smoother character gives him a makeover.

"It was very fun to dive into these characters and see who could they be," Cooper said. "My heart goes out to all of them, especially Richie. There's nothing like watching somebody lose their innocence. It's my job as an actor to make that fresh and personal."

"He was rewriting while the cameras were rolling, a process that's unique," Cooper said. "No one really knows what's happening but him. I love it because it gets you out of your head. It makes things easier, because it just forces you to react."

Cooper's father, a stockbroker, wasn't convinced that an acting career was a sound business plan for his son. Cooper had his own moments of doubt.

In 1999, when he was 23, he worked as a doorman on the graveyard shift at the fashionable Morgan Hotel in New York City.

"One of the guys I took to their rooms was Leonardo DiCaprio," fresh off his superstar turn in Titanic, Cooper said.

"I remember riding down on the elevator after I showed him and about seven of his friends their room. I was wearing the uniform, not a hip look. I remembered reading recently that he and I were exactly the same age. I went down in the elevator thinking I had been four feet from the guy and we couldn't be in two more different worlds. He was my age and he had accomplished so much."

It sure is. Next year Cooper will become a figure in the Marvel superhero universe, but with a lunatic twist.

In Guardians of the Galaxy, he plays pint-size Rocket Raccoon, a gun-slinging, genetically manipulated critter with an advanced intellect and humanoid properties. He's working with director James Gunn to perfect the militant little furball's sound. (A tough Cockney accent is under consideration.)

Cooper is also working out the digitally rendered creature's body language, acting out his scenes in a bodysuit as motion-capture cameras record his performance.

"We're right in the middle of it, but I can say he's a pretty volatile guy." Playing a wisecracking extraterrestrial ringtail might seem like a pretty big stretch, but so far underestimating Cooper has been a bad bet.